Ann Arbor works on speeding up its traffic. It has reduced weekday travel times on affected corridors by 12 percent, and weekend travel time by 21 percent. The system not only is able to sense if a vehicle is stopped, and turn the light green to help it along. It knows how many vehicles are stopped, in which lane, and how many vehicles are coming down the pike.
The system relies on pavement-embedded sensors or cameras to spot cars waiting at red lights. The signals send that information via fiber network to the Big Computer back at traffic management base, which compiles the data.
This stuff works on a macro and micro level: If there are four cars lined up to go one way through an intersection, and zero cars lined up to move perpendicular to them, the light might turn green for the four. But a network of connected lights—like in Ann Arbor—will analyze the entire grid, and figure out who to prioritize to get the most people to their destinations the fastest. Advanced traffic control systems can even predict delays and congestion build-up before they happen, based on the ebb and flow of commutes.